A novel dual‐band F‐shaped monopole antenna is proposed. The antenna comprises a vertical metal line and two (one upper and one lower) horizontal metal lines of different lengths, which are used for tuning the antenna's first two resonant frequencies to achieve desired dual‐band operation. The proposed antenna is very suitable to be printed on a microwave substrate and can be easily integrated with the associated circuitry on the same substrate. A constructed prototype suitable for wireless LAN applications in the 2.4‐ and 5.2‐GHz bands is demonstrated. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 24–26, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10362

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User's hand effects on an electromagnetic‐compatible (EMC) internal dual‐band mobile phone antenna for GSM/DCS operation are studied. The EMC internal antenna can be placed in direct contact with nearby conducting elements, without degradation in the antenna performances. Experimental and simulation studies are conducted to analyze the user's hand effects on this EMC antenna. Obtained results indicate that the user's hand affects not only the impedance matching of the antenna, but also the radiation characteristics including radiation patterns and efficiency. Effects of different positions of the user's hand holding the mobile phone are also analyzed and discussed. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1563–1569, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21699

In this study, we presented and applied a focusing method based on hyperbolic summation (HS) technique to the simulated and measured B-scan GPR data generated via a SFR system, especially tested at C-band frequencies. The methodology was explained in detail and both numerical and measured examples, testing the effectiveness of the method, were presented. Application of the proposed method to the examples demonstrated that pipes and point scatterer-like objects produce very well-focused images in the new GPR image. This is due to the fact that the method uses hyperbolic templates corresponding to point-scatterers and converts these hyperbolas to single image pixels. The plate-like objects in the numerical examples also successfully produced wellfocused images. In terms of computational efficiency, the algorithm is fast for 2-D B-scan images. It is clear that, the method can easily be adapted to 3-D C-scan images with hyperbolic surface templates. The method is examined with an SFR experimental set-up and measured B-scan GPR data. Both the traditional and the focused B-scan images were generated after applying the proposed method. Acceptable success has been achieved for the measured data as well.The main weakness of the method becomes apparent for the case if any scattering mechanism falls under the hyperbolic template of another greater scattering, this point will produce a smaller scattering than its original EM energy in the final GPR image. Therefore, the energy levels in the final focused image will not correspond to the true energy levels of each scatterer. The other drawback of the method is that it produces ghost tails from the focused point toward upper regions as explained in Section 4. This phenomenon can be observed from Figure 5(b).In this work, we only considered homogeneous and nearly lossless mediums. For inhomogeneous, lossy, and anisotropic mediums, the applicability of the method would be limited as the velocity and the wave number of the EM wave changes as the wave travels. Therefore, a model-based focusing method should be adopted for such soils.

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other two. Considering that radiation fog has the smallest particlesize distribution, our results should stand for this type of fog as well. Although we do not know the exact particle-size distribution of the fog in the measured link, the upslope fog is similar in formation to the advection fog; therefore, we also believe that, for this type of fog, the performance of the far-IR link should not be worse than those of the other two. Of course, present-day commercial technology still benefits shorter wavelengths, mostly due to the availability of low-cost sources and detectors. However, new technologies can produce competing devices for the far-IR window; thus our results demonstrate that it is worth working in the development of appropriate devices and systems because the optical channel indeed performs better at long wavelengths in most cases. ACKNOWLEDGMENTSThis work was supported by the Research and Development Center of Ericsson Telecomunicações S/A, Brazil, and C. P. Colvero acknowledges scholarship support from the Brazilian Agency CNPq. The authors acknowledge the Brazilian state companies TVE Brasil and Furnas Centrais Elétricas S/A for allowing the installation of the transmitters and receivers within their facilities. INTRODUCTIONDue to the recent successful deployment of wireless local area networks (WLANs) in numerous hotspots, it has become promising to integrate cellular and WLAN networks to provide ubiquitous or seamless data services for users [1, 2]. For this kind of integrated cellular/WLAN network application, it is expected that mobile phones or PDA phones capable of dual-network operation will become popular in the near future. For this promising application, many of the dual-network mobile or PDA phones are generally equipped with two antennas, one for cellular operation and another for WLAN operation. In this case, since there are limited spaces available inside the portable devices, isolation between the two antennas has become a critical issue. However, very little related information is available in the open literature.Recently, a study on the isolation between two promising internal antennas-one GSM/DCS (890 -960 MHz/1710 -1880 MHz) antenna and one 2.4-GHz (2400 -2484 MHz) WLAN antenna [3]-for a dual-network PDA phone has been presented [4]. The results have shown that with the GSM/DCS antenna fixed at the top edge of the system circuit board, optimized or nearoptimized isolation is achieved when the WLAN antenna is placed near the bottom edge of the system circuit board. In this study, the maximum isolation S 21 values over the GSM, DCS, and WLAN bands are less than Ϫ33.6, Ϫ27.9, and Ϫ33.0 dB, respectively, which are quite good for practical applications [4]. However, in this case, the two antennas need to be separated by a relatively large distance. In this paper, we present an isolation study that considers two promising internal GSM/DCS and WLAN antennas printed and integrated on a dielectric substrate. In the study, both of the GSM/DCS and WLAN antennas are printed PIFAs of compact...

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